The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
A gasoline internal combustion engine (ICE) typically includes an exhaust system with a catalytic converter. The exhaust system may also include a gasoline particulate filter (GPF) downstream from the catalytic converter. The GPF filters soot and particulates from an exhaust gas output from the gasoline ICE.
During operation of a gasoline ICE, a level of oxygen (O2) in a GPF of the gasoline ICE can be below a level needed to oxidize soot in the GPF. In addition, a temperature of an exhaust gas received by the GPF can be in a temperature range (e.g., at a temperature less than a predetermined temperature) that is not conducive for soot oxidation. Thus, regeneration of the GPF may not be performed and/or may not be efficiently performed during certain operating conditions. Inefficient regeneration can also occur during fuel cut off events when there is an abundance of oxygen (O2) in the GPF but the GPF is no at a sufficient temperature for oxidation. Examples of fuel cut off events are clutch fuel cut off (CFCO) events and deceleration fuel cut off (DFCO) events. Fuel cut off events can occur as a result of cylinder deactivation. A cylinder deactivation system may deactivate one or more cylinders of an engine during operation of the engine to conserve fuel.
DFCO is used for various reasons. DFCO may be used to provide deceleration (powertrain braking) force when an accelerator of a vehicle is not actuated (e.g., vehicle operator does not press on accelerator pedal). In high elevation (mountainous) areas and/or areas with large variations in elevation, DFCO is used to provide powertrain braking to avoid damage to friction brakes of a vehicle.
DFCO may also be used to prevent damage to a catalytic converter. For example, a throttle position may be calibrated and fixed to provide a minimal amount of air-per-cylinder (APC) to an engine, thereby providing vehicle deceleration when traveling downhill. Due to the fixed throttle position and/or a manual pull down of a transmission (PRNDL) shifter (e.g., shift into a low gear, such as L1 or L2), the APC levels of the ICE can become too low and cause a misfire. A misfire refers to incomplete combustion of an air/fuel mixture in a cylinder of the engine. This misfire can result in fuel entering and igniting in an exhaust system, which increases temperature of a catalyst of the catalytic converter. Damage to the catalyst can occur when temperatures of the catalyst exceed a threshold. By using DFCO, fuel is disabled, which protects the catalyst from misfire events.
DFCO may also be used to increase fuel economy. The efficiency of a gasoline spark ignited engine can be low at minimum combustion (i.e. minimum air and fuel levels) because of pumping losses and other factors. Disabling the fuel is more efficient than reducing the amount of fuel to an ICE.